Variable speed pyrolytic waste treatment system

ABSTRACT

The inventive subject matter is directed toward a pyrolytic waste treatment system comprising a pyrolysis chamber and a movement mechanism adapted to move waste through the pyrolysis chamber at different speeds along the length of the pyrolysis chamber.

This application claims the benefit of U.S. patent application Ser. No. 10/923,183 filed on Aug. 19, 2004 which claims priority to provisional application No. 60/497397 filed on 21 Aug. 2003 incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The field of the invention is pyrolytic waste treatment.

BACKGROUND OF THE INVENTION

Pyrolysis is a known method for treatment of waste. Examples of pyrolytic waste treatment systems can be found in U.S. Pat. Nos. 4,759,300, 5,653,183, 5,868,085, and 6,619,214. Unlike incineration, pyrolysis is the destructive decomposition of waste materials using indirect heat in the absence of oxygen. Burning wastes through incineration with direct flame in the presence of oxygen can be explosive, causing turbulence in the burning chamber, which fosters a recombination of released gases. Waste destruction in an oxygen-rich atmosphere makes conversion far less complete, is highly inefficient and creates harmful substances.

In contrast, the pyrolytic process employs high temperature in, most desirably, an atmosphere substantially free of oxygen (for example, in a practical vacuum), to convert the solid components of waste to a mixture of solids, liquids, and gases with proportions determined by operating temperature, pressure, oxygen content, and other conditions. The solid residue remaining after pyrolysis commonly is referred to as char. The vaporized product of pyrolysis is often further treated by a process promoting oxidation, which “cleans” the vapors to eliminate oils and other particulate matter there from, allowing the resultant gases then to be safely released to the atmosphere.

What has long been needed and heretofore has been unavailable is an improved pyrolytic waste treatment system that is highly efficient, is easy to maintain, is safe, reliable and capable of operation with a wide variety of compositions of waste materials, and that can be constructed and installed at relatively low cost. The thrust of the present invention is to provide such an improved pyrolytic waste treatment system.

SUMMARY OF THE INVENTION

The present subject matter is directed toward a pyrolytic waste treatment system in which a movement mechanism is used to move waste through the pyrolysis chamber at various rates along the length of the pyrolysis chamber.

In another aspect, a method of pyrolyzing waste in an elongated chamber comprises moving the waste through the chamber at different rates along the length of the chamber.

Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic of a pyrolytic waste treatment system.

FIG. 2 is a perspective view of a mechanism having screw and paddles.

FIG. 3 is a perspective view of a mechanism having screw and paddles.

FIG. 4 is a perspective view of a mechanism having screw and paddles.

FIG. 5 is a cross sectional view of mechanism in FIG. 4.

FIG. 6 is a cross sectional view of mechanism in FIG. 4.

FIG. 7 is a cross sectional view of mechanism in FIG. 4.

FIG. 8 is a perspective view of a mechanism having screw and paddles.

FIG. 9 is a perspective view of a mechanism having screw and paddles.

FIG. 10 is a perspective view of a mechanism having screw and a paddle.

FIG. 11 is a perspective view of a mechanism having screw and paddles.

FIG. 12 is a top view of a dual-mechanism system having screw and paddles.

FIG. 13 is a perspective view of the brushes.

FIG. 14 is another perspective view of the brushes.

DETAILED DESCRIPTION

In FIGS. 1 and 2, a pyrolytic waste treatment system 100 generally comprises a pyrolytic chamber 110 and a waste movement mechanism 160.

It is contemplated that it would be beneficial to vary the rate of movement of material through a pyrolysis chamber. In particular, material might move at a slower rate when it first enters the chamber and move at a faster rate after it has been heated and as is moved toward the chamber exit. It is contemplated that the use of paddles 171 or a screw 161 in which the pitch of the paddles 171 or the screw 161 threads varies from one end of the chamber to the other would prove beneficial. It should be recognized that other methods and devices may be used to move material through the chamber including, for example, using gravity, magnetism, and forced air. With regard to using magnetism, it is further contemplated that a product could be statically charged within a magnetic field. Other methods and devices are also contemplated so long as they move the product through the chamber and are in accordance with the inventive concepts described herein. In FIG. 1, the paddles 171 are disposed every 90 degrees and are straight, or substantially parallel to the center longitudinal axis of the drive shaft 169. This paddle design keeps waste in the chamber at a relative consistent residence time throughout the length of the section 112.

It is preferred that the speed at which waste moves through the chamber 110, and the temperature of the chamber 110 will both vary along the length of the chamber 110. At least in part in order to minimize heat loss, the ends of the chamber are generally cooler than portions of the chamber closer to the center of the chamber. As such, waste movement mechanism 160 varies along the length of pyrolysis chamber 110 to increase movement speed at the cooler ends, and to slow it down in the active heating region.

In section 111 of chamber 110, mechanism 160 comprises screw conveyor section 161 adapted to move waste quickly through section 111 away from waste inlet 130. In section 112, where active heating occurs, mechanism 160 comprises a first paddle section 162, wherein the paddles are oriented primarily to agitate, mix, and expose waste to heat rather than move it along the chamber 110. Movement of waste through section 112 occurs to a large extent from being pushed by waste moving into section 112 from section 111. In section 113, a second paddle section 163 has paddles oriented to move waste along section 113 to char outlet 140. Further examples to the orientations of the paddles are shown in FIG. 3. The screw conveyer and paddles are coupled to, and may be integrally formed with, a drive shaft 169.

Screw conveyor section 161 of mechanism 160 is in some embodiments about 5 feet long, and the screw blades are pitched at varying degrees. In some embodiments, section 162 is about 20 feet long, and comprises approximately 42 paddles, wherein at least some of the paddles are oriented such that at least one side is substantially parallel to the center axis of shaft 169. In contrast, the section 163 of mechanism 160 (in some embodiments the last 5 feet of mechanism 160) of paddles system are pitched/angled to move the waste that has already reached the proper temperature quickly out of the actively heated zone.

In FIG. 3, drive shaft 169 rotates in direction R. Sections A of paddles 171 correlates to the pitch and angle of section 162. Sections A works to move waste forward. Other the other hand, sections B of paddles 171 correlates to the pitch and angle of section 163, and work primarily to agitate, mix, and expose waste to heat rather than move it along the chamber. This design keeps waste in the chamber for a relatively longer residence time.

In FIG. 4, drive shaft 169 rotates in direction R. Paddles 171 are disposed every 120 degrees and are not pitched. This design works primarily to agitate, mix, and expose waste to heat rather than move it along the chamber.

FIGS. 5-7 illustrate positions of paddles 171 in FIG. 4.

FIGS. 8-11 illustrate different placement, pitch, and shape of the paddles 171. FIG. 8 shows a “plow” design of paddles 171 to keep carbon char intact while conveying. In FIG. 9, “scoop” design is shown to keep char intact while conveying. The “scoop” paddles 171 also scoops the char off of the chamber floor. In FIG. 10, a single longitudinal paddle 171 is shown to mix the char while the incoming waste pushes the waste through the chamber. FIG. 11 shows paddles at a slight pitch, creating a shorter residence time within the retort chamber.

FIG. 12 illustrates a dual mechanism design where two mechanisms 160 lay side-by-side with varied pitch and angles to the screw 161 and paddles 171. The mechanisms rotate in different directions. In other preferred embodiments, the two mechanisms can rotate in the same direction.

FIGS. 13 and 14 disclose brushes 172 disposed on the trailing side of the paddle 171, on mechanism 160. These brushes advantageously keep the floor of the chamber relatively free of waste. FIG. 14 shows brushes positioned on the trailing side of the paddle 171, giving the brush sufficient room to flex when cleaning the chamber floor/wall. Brushes can be positioned on the trailing side or on the leading side of paddle 171. Alternatively, brushes can be positioned on neither the trailing side nor on the leading side of paddle 171. Brushes can work independently without having paddles on mechanism, or without paddles positioned adjacent to the brushes 172. It is contemplated that the brush can be used on any paddle design.

Although a movement mechanism comprising a screw and paddles mounted to a single drive shaft is shown, alternative embodiments may use alternative apparatus and or methods to vary the speed at which material moves through pyrolysis chambers. As an example, some embodiments may utilize multiple movement mechanisms rather than a single movement mechanism. Others may utilize paddles along the entire length of the chamber, may utilize paddles followed by a screw conveyor, may utilize only a screw conveyer, or may utilize an entirely different type of mechanism such as one or more flat conveyers.

A pyrolytic waste treatment system, particularly a continuous feed system adapted to move waste being treated at different speeds along the length of a pyrolysis chamber. Variances in speed may result from varying the pitch of paddles and/or screws used to move the waste along the length of the pyrolysis chamber.

Energy savings and improved treatment can be achieved in a pyrolysis treatment system which varies the rate of movement of material through a pyrolysis chamber. In particular, material moving material at a slower rate when towards the center of the chamber relative to when it first enters the chamber and when it approaches the chamber exit minimizes heat losses at the chamber entrance and exit while insuring the waste is adequately heated for treatment. Varying the rate of movement may be achieved through the use of paddles or a screw in which the pitch of the paddles or the screw threads varies from one end of the chamber to the other.

Thus, specific embodiments and applications of a pyrolytic system have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. 

1. A pyrolytic waste treatment system, comprising: a pyrolysis chamber; a first rotating common shaft disposed within the the pyrolysis chamber; a screw blade disposed on a first section of the common shaft adapted to move a waste through the pyrolysis chamber at a first speed partially determined by a first pitch of the blade; a first paddle disposed on the common shaft having a second pitch to move waste at a second speed; a second paddle disposed on the common shaft having a third pitch to move waste at a third speed; and wherein the second pitch and the third pitch are angled differently from each other such that the second speed and third speed are also different from each other.
 2. The system of claim 1, wherein at least one of the first, second, or third pitch is angled to move the waste through the pyrolysis chamber at a faster rate near an inlet and an outlet of the chamber relative to a center portion of the chamber.
 3. The system of claim 1, wherein the first pitch is varied along the length of the screw blade to move the waste at different speeds along a length of the first section.
 4. The system of claim 1, wherein in the second pitch is angled to move the waste through the pyrolysis chamber in a direction towards a waste inlet, and the third pitch is angled to move the waste through the pyrolysis chamber in a direction away from the waste inlet.
 5. The system of claim 1 further comprising a brush disposed on the common shaft to brush against a chamber wall of the pyrolysis chamber.
 6. The system of claim 1 further comprising a second rotating common shaft disposed adjacent and parallel to the first rotating common shaft within the pyrolysis chamber.
 7. A pyrolytic waste treatment system, comprising: a pyrolysis chamber; a rotating common shaft disposed within the pyrolysis chamber; a screw blade disposed on the common shaft adapted to move a waste through the pyrolysis chamber at a speed partially determined by a first pitch of the blade; a paddle disposed on the common shaft wherein the paddle has a general configuration that is substantially parallel to a center axis of the common shaft; and wherein the general configuration increases a residence time of the waste in the chamber.
 8. The system of claim 7, wherein the general configuration is a scoop.
 9. The system of claim 7, wherein the general configuration is a plow.
 10. The system of claim 7, wherein the general configuration is a flat panel.
 11. A method of pyrolyzing waste in a pyrolysis chamber comprising: providing a movement mechanism disposed within the chamber adapted to move a waste through the chamber at different rates of speed; wherein the movement mechanism comprises a rotating common shaft; wherein the movement mechanism further comprises a screw conveyer, a first paddle, and a second paddle, all of which are coupled to the common shaft; wherein the first paddle is angled to move the waste towards an outlet at a first speed; and wherein the second paddle is angled to move the waste towards an outlet at a second speed slower than the first speed.
 12. The method of claim 11 further comprises increasing a waste residence time by having a second paddle angled to move waste in a direction towards an inlet.
 13. The method of claim 11 further comprises increasing a waste residence time by having a second paddle oriented substantially parallel to a center axis of the common shaft.
 14. The method of claim 11 further comprises keeping a carbon char intact by using a scoop configuration for the first paddle.
 15. The method of claim 11 further comprises keeping a carbon char intact by using a plow configuration for the first paddle.
 16. The method of claim 11 further comprises keeping a chamber floor relatively free of waste by brushing the chamber floor with a brush disposed on the common shaft. 